An Alternating Current (AC) Contactor, widely used in power switching and control circuits, is a type of contactor. These contactors can be categorized into industrial contactors and building/domestic contactors.

AC Contactor

Working Principle of AC Contactors
AC contactors operate by opening and closing circuits using main contacts and executing control commands through auxiliary contacts. Main contacts are generally normally open, while auxiliary contacts often include a pair of normally open and normally closed contacts. Small contactors are also frequently used as intermediate relays in main circuits.

In electrical engineering, due to their ability to quickly disconnect AC and DC main circuits and frequently connect with high current control circuits (some models up to 800 amperes), they are commonly used to control electric motors, as well as factory equipment, electric heaters, mother machines, and various power loads. Contactors not only connect and disconnect circuits but also offer low-voltage release protection. They are suitable for frequent operations and long-distance control.

AC contactors are crucial components in automatic control systems. In industrial electricity, there are many types of contactors, ranging from 5A to 1000A, serving a wide array of purposes.

AC Contactor

Contactors can be broadly divided into two categories:

AC Contactors: Comprising electromagnetic mechanisms, contact systems, and arc extinguishing devices. Common models include CJ10, CJ12, CJ12B, etc.
DC Contactors: Generally used to control DC electrical devices, their operating principles and structures are fundamentally similar to AC contactors.
Structure Description
AC contactors mainly consist of electromagnetic systems, contact systems, arc extinguishing systems, and other components.

Electromagnetic System: Includes an electromagnetic coil and core, essential for opening and closing contacts.
Contact System: The executing part, consisting of main and auxiliary contacts. Main contacts connect and disconnect the main circuit, controlling larger currents, while auxiliary contacts fulfill various control requirements.
Arc Extinguishing System: Ensures reliable extinguishing of arcs generated during contact separation, minimizing damage.
Other Components: Include an insulating shell, springs, short-circuit rings, and transmission mechanisms.
Issues and Solutions for Unreliable Contact
Reasons for unreliable contact in contactors and their solutions

AC Contactor


Oil, fluff, foreign matter on contacts; long-term use leading to oxidation; arc erosion causing defects, burrs, or metal chips; obstruction in moving parts.


Clean contacts with alcohol or gasoline for oil and foreign matter; for silver or silver alloy contacts, clean with alcohol, gasoline, or carbon tetrachloride solutions. Use fine files for slight burns or blackening, but avoid over-filing. For copper contacts, lightly file uneven areas, but avoid sandpaper to prevent quartz sand particles from remaining. Replace severely burnt contacts. For obstructed moving parts, disassemble and repair.”

AC Contactor
Silent AC Contactors are essential for efficient power control in various electrical applications. Understanding their structure, types, and common issues, along with appropriate troubleshooting methods, ensures their effective and safe operation. Regular maintenance and correct handling of contactor components are crucial for their longevity and reliability in both industrial and domestic settings.